The invention relates generally to lowering the amount of carbon monoxide and/or nitric oxide in the mainstream smoke of a cigarette during smoking. More specifically, the invention relates to cut filler compositions, cigarettes, methods for making cigarettes and methods for smoking cigarettes, which involve the use of manganese oxide mixtures. These mixtures include manganese oxide with other additive(s) capable of converting carbon monoxide to carbon dioxide and/or converting nitric oxide to nitrogen in nanoparticle form.
Various methods for reducing the amount of carbon monoxide and/or nitric oxide in the mainstream smoke of a cigarette during smoking have been proposed. For example, British Patent No. 863,287 describes methods for treating tobacco prior to the manufacture of tobacco articles, such that incomplete combustion products are removed or modified during smoking of the tobacco article. This is said to be accomplished by adding a calcium oxide or a calcium oxide precursor to the tobacco. Iron oxide is also mentioned as an additive to the tobacco.
Cigarettes comprising absorbents, generally in a filter tip, have been suggested for physically absorbing some of the carbon monoxide, but such methods are usually not completely efficient. A cigarette filter for removing byproducts formed during smoking is described in U.S. Reissue Pat. No. RE 31,700, where the cigarette filter comprises dry and active green algae, optionally with an inorganic porous adsorbent such as iron oxide. Other filtering materials and filters for removing gaseous byproducts, such as hydrogen cyanide and hydrogen sulfide, are described in British Patent No. 973,854. These filtering materials and filters contain absorbent granules of a gas-adsorbent material, impregnated with finely divided oxides of both iron and zinc. In another example, an additive for smoking tobacco products and their filter elements, which comprises an intimate mixture of at least two highly dispersed metal oxides or metal oxyhydrates, is described in U.S. Pat. No. 4,193,412. Such an additive is said to have a synergistically increased absorption capacity for certain substances in the tobacco smoke. British Patent No. 685,822 describes a filtering agent that is said to oxidize carbon monoxide in tobacco smoke to carbonic acid gas. This filtering agent contains, for example, manganese dioxide and cupric oxide, and slaked lime. The addition of ferric oxide in small amounts is said to improve the efficiency of the product.
The addition of an oxidizing reagent or catalyst to the filter has been described as a strategy for reducing the concentration of carbon monoxide reaching the smoker. The disadvantages of such an approach, using a conventional catalyst, include the large quantities of oxidant that often need to be incorporated into the filter to achieve considerable reduction of carbon monoxide. Moreover, if the ineffectiveness of the heterogeneous reaction is taken into account, the amount of the oxidant required would be even larger. For example, U.S. Pat. No. 4,317,460 describes supported catalysts for use in smoking product filters for the low temperature oxidation of carbon monoxide to carbon dioxide. Such catalysts include mixtures of tin or tin compounds, for example, with other catalytic materials, on a microporous support. Another filter for smoking articles is described in Swiss patent 609,217, where the filter contains tetrapyrrole pigment containing a complexed iron (e.g. haemoglobin or chlorocruorin), and optionally a metal or a metal salt or oxide capable of fixing carbon monoxide or converting it to carbon dioxide. In another example, British Patent No. 1,104,993 relates to a tobacco smoke filter made from sorbent granules and thermoplastic resin. While activated carbon is the preferred material for the sorbent granules, it is said that metal oxides, such as iron oxide, may be used instead of, or in addition to the activated carbon. However, such catalysts suffer drawbacks because under normal conditions for smoking, catalysts are rapidly deactivated, for example, by various byproducts formed during smoking and/or by the heat. In addition, as a result of such localized catalytic activity, such filters often heat up during smoking to unacceptable temperatures.
Catalysts for the conversion of carbon monoxide to carbon dioxide are described, for example, in U.S. Pat. Nos. 4,956,330 and 5,258,330. A catalyst composition for the oxidation reaction of carbon monoxide and oxygen to carbon dioxide is described, for example, in U.S. Pat. No. 4,956,330. In addition, U.S. Pat. No. 5,050,621 describes a smoking article having a catalytic unit containing material for the oxidation of carbon monoxide to carbon dioxide. The catalyst material may be copper oxide and/or manganese dioxide. The method of making the catalyst is described in British Patent No. 1,315,374. Finally, U.S. Pat. No. 5,258,340 describes a mixed transition metal oxide catalyst for the oxidation of carbon monoxide to carbon dioxide. This catalyst is said to be useful for incorporation into smoking articles.
Transition metals have been described for use in cigarette filters or smoking articles. U.S. Pat. No. 3,407,820 describes a tobacco smoke filter containing manganese (IV) oxide dihydroxide for the purpose of removing nitrogen oxides from smoke. British Patent No. 685822 describes filtering agents, where carbon monoxide in tobacco smoke is converted to carbon dioxide, by passing it over metal oxides, including manganese dioxide and cupric oxide, kept dry by admixture with, e.g. three times the quantity of, slaked lime. U.S. Pat. No. 4,125,118 states that the amounts of tars, nicotine, phenols, carbon monoxide, hydrogen cyanide, etc. generated during the smoking of tobacco and its substitutes is reduced by incorporating in the smoking composition a small amount of a transition metal compound.
Metal oxides, such as iron oxide have also been suggested for use in cigarettes for various purposes. For example, in WO 87/06104, the addition of small quantities of zinc oxide or ferric oxide to tobacco is described, for the purposes of reducing or eliminating the production of certain byproducts, such as nitrogen-carbon compounds, as well as removing the stale xe2x80x9cafter tastexe2x80x9d associated with cigarettes. The iron oxide is provided in particulate form, such that under combustion conditions, the ferric oxide or zinc oxide present in minute quantities in particulate form is reduced to iron. The iron is claimed to dissociate water vapor into hydrogen and oxygen, and cause the preferential combustion of nitrogen with hydrogen, rather than with oxygen and carbon, thereby preferentially forming ammonia rather than the nitrogen-carbon compounds.
In another example, U.S. Pat. No. 3,807,416 describes a smoking material comprising reconstituted tobacco and zinc oxide powder. Further, U.S. Pat. No. 3,720,214 relates to a smoking article composition comprising tobacco and a catalytic agent consisting essentially of finely divided zinc oxide. This composition is described as causing a decrease in the amount of polycyclic aromatic compounds during smoking. Another approach to reducing the concentration of carbon monoxide is described in WO 00/40104, which describes combining tobacco with loess and optionally iron oxide compounds as additives. The oxide compounds of the constituents in loess, as well as the iron oxide additives are said to reduce the concentration of carbon monoxide.
Moreover, iron oxide has also been proposed for incorporation into tobacco articles, for a variety of other purposes. For example, iron oxide has been described as particulate inorganic filler (e.g. U.S. Pat. Nos. 4,197,861; 4,195,645; and 3,931,824), as a coloring agent (e.g. U.S. Pat. No. 4,119,104) and in powder form as a burn regulator (e.g. U.S. Pat. No. 4,109,663). In addition, several patents describe treating filler materials with powdered iron oxide to improve taste, color and/or appearance (e.g. U.S. Pat. Nos. 6,095,152; 5,598,868; 5,129,408; 5,105,836 and 5,101,839). Chinese Patent No. 1312038 describes a cigarette comprising iron and iron oxide (including FeO, Fe2O3, Fe3O4, and ferrite) as additives for reducing stimulant and abnormal smell of smoke and reducing certain components of smoke. However, the prior attempts to make cigarettes incorporating metal oxides, have not led to the effective reduction of carbon monoxide in mainstream smoke.
Despite the developments to date, there remains a continued interest in improved and more efficient methods and compositions for lowering the amount of carbon monoxide and/or nitric oxide in the mainstream smoke of a cigarette during smoking. Preferably, such methods and compositions should not involve expensive or time consuming manufacturing and/or processing steps. More preferably, it should be possible to convert carbon monoxide to carbon dioxide and/or convert nitric oxide to nitrogen not only in the filter region of the cigarette, but also along the length of the cigarette during smoking.
The invention relates to cut filler compositions, cigarettes, methods for making cigarettes and methods for smoking cigarettes which involve the use of manganese oxide mixtures, which include manganese oxide with other additive(s) capable of converting carbon monoxide to carbon dioxide and/or converting nitric oxide to nitrogen in nanoparticle form.
In an embodiment of the invention, cut filler compositions are provided, which comprise tobacco, manganese oxide, and at least one additive capable of converting carbon monoxide to carbon dioxide and/or converting nitric oxide to nitrogen, wherein the manganese oxide and the additive are both in the form of nanoparticles.
In another embodiment of the invention, cigarettes are provided, which comprise a tobacco rod that comprises cut filler having manganese oxide and at least one additive capable of converting carbon monoxide to carbon dioxide and/or converting nitric oxide to nitrogen. The manganese oxide and the additive are both in the form of nanoparticles. In one embodiment, a cigarette according to the invention contains manganese oxide and the additive in a total amount from about 5 mg per cigarette to about 100 mg per cigarette, or in a total amount from about 40 mg per cigarette to about 50 mg per cigarette
In another embodiment of the invention, methods for making cigarettes are provided, which comprise:
(i) adding manganese oxide and at least one additive capable of converting carbon monoxide to carbon dioxide and/or converting nitric oxide to nitrogen to a cut filler, wherein the manganese oxide and the additive are both in the form of nanoparticles;
(ii) providing the cut filler comprising the manganese oxide and additive to a cigarette making machine to form a tobacco rod; and
(iii) placing a paper wrapper around the tobacco rod to form the cigarette.
In an embodiment of the invention, the manganese oxide can be co-precipitated with the additive prior to (i) above, or mechanically mixed with the additive prior to (i) above.
In yet another embodiment of the invention, methods for smoking the cigarettes according to the invention are provided, which involves lighting the cigarette to form smoke and drawing the smoke through the cigarette, wherein during the smoking of the cigarette, the manganese oxide and/or the additive convert carbon monoxide to carbon dioxide and/or convert nitric oxide to nitrogen.
Preferably, the additive used with the manganese oxide is capable of converting carbon monoxide to carbon dioxide and converting nitric oxide to nitrogen. The additive may be selected from the group consisting of metal oxides, doped metal oxides, and mixtures thereof. For instance, the additive may be selected from the group consisting of Fe2O3, CuO, TiO2, CeO2, Ce2O3, Al2O3, Y2O3 doped with zirconium, Mn2O3 doped with palladium, and mixtures thereof. Preferably, the additive comprises Fe2O3.
Preferably, the manganese oxide has a lower light-off temperature than the additive, such that during smoking of the cigarette, the heat generated from the oxidation of carbon monoxide by manganese oxide activates the additive.
The manganese oxide may be combined with the additive in any suitable manner. For example, the manganese oxide may be co-precipitated with the additive, or it may be mechanically mixed with the additive.
In an embodiment of the invention, the manganese oxide and the additive both have an average particle size less than about 500 nm, more preferably less than about 100 nm, even more preferably less than about 50 nm, and most preferably less than about 5 nm. Preferably, the manganese oxide and the additive both have a surface area from about 20 m2/g to about 400 m2/g, or more preferably from about 200 m2/g to about 300 m2/g.
The manganese oxide and the additive are typically used in an amount effective to convert at least 50%, or more preferably at least 80% of the carbon monoxide to carbon dioxide and/or at least 50%, or more preferably at least 80% of the nitric oxide to nitrogen.